Against the backdrop of global warming and exhaustion of fossil resources, production of chemical products using renewable resources, along with production of biofuels, is recognized as an emerging industry, biorefinery, which is an important means for realizing a low-carbon society, and has attracted keen attention.
Valine, which is one of the essential amino acids, is a useful substance as an ingredient of medicaments, foods, and cosmetics, or as an additive for animal feed, etc. Conventionally, valine is produced by a fermentation method or hydrolysis of proteins.
However, production of valine from renewable resources by a fermentation method is less productive as compared to production of lactic acid or ethanol for the reasons, for example, that the metabolic reaction from a raw material sugar consists of a great many steps and that produced valine causes feedback inhibition of metabolic enzymes, posing problems in industrial production.
Examples of known valine-producing technologies with the use of recombinant bacteria include the technologies described in Patent Literature 1 and 2.
Patent literature 1 discloses a technology for producing valine using a mutant strain of Corynebacterium glutamicum in which a gene encoding an enzyme involved in L-isoleucine biosynthesis, a gene encoding an enzyme involved in L-leucine biosynthesis, and a gene encoding an enzyme involved in D-pantothenic acid biosynthesis are weakened or deleted for an increased expression of a gene encoding an enzyme involved in L-valine biosynthesis.
Patent literature 2 discloses a technology for producing valine using a strain of Corynebacterium having an improved activity of transaminase C.
However, the processes of Non Patent Literature 1 and 2 do not have practically sufficient valine productivity.